Aerofoil members are used in fluid dynamic applications such as wings for aeroplanes, watercraft, flying wings, unmanned aerial vehicles (UAVs), and fins for projectiles.
It is desirable to be able to change the profile shape of an aerofoil in order to effect control of aerodynamic forces, for example to control the movements of a vehicle, and also in order to adjust the aerodynamic forces to suit different conditions (for example at different speeds). This is conveniently achieved with movable surfaces such as ailerons, flaps and airbrakes. However the effect of these on the characteristics of the aerofoil is limited by the fact that they change only a small part of the aerofoil shape.
The use of an adaptive structure able to change the shape of an aerofoil member, for example a “morphing wing”, has the potential to reduce the system complexity by eliminating control surfaces and their associated equipment. It also has the potential to allow a flying body such as a UAV to adapt to the varying conditions experienced during flight by providing an optimal aerofoil sectional shape over a range of speeds, for example transonic flight.
Prior attempts to eliminate control surfaces have focused on attempting to bend the outer surface or skin of the aerofoil. For example, bending the skin downwardly along the trailing edge of a wing might mimic an aileron effect. A problem with this approach is that the elements used to affect the bending must be very stiff, so that in practice it is difficult to achieve a sufficiently large movement, and thus a sufficient control effect.